English organizes time prepositions into a tidy three-way system: at a clock time, on a day, in a month or year. Portuguese carves up time completely differently, and almost none of the boundaries line up. Em covers months, years, and seasons; a/às covers clock times; de covers parts of the day; and an entirely separate pair — há and daqui a — handles "ago" versus "from now," a distinction English collapses awkwardly into ago and in. The single most important thing on this page is that last split: get há dois anos (two years ago) and daqui a dois anos (two years from now) straight, and you've cleared the biggest trap.
em — months, years, seasons, durations
Em is the default for larger time units: years, months, seasons, and "within X amount of time." With the definite article it contracts (em + o = no, em + a = na).
Ela nasceu em 1998, em pleno inverno.
She was born in 1998, in the dead of winter.
As aulas começam em fevereiro.
Classes start in February.
A gente se muda no verão, quando esfria um pouco.
We're moving in the summer, when it cools down a bit. (em + o = no)
Termino o relatório em três dias.
I'll finish the report in three days. (within three days)
Seasons take the article (no verão, na primavera), but bare months and years do not (em março, em 2025). And em três dias means within three days — don't confuse it with daqui a três dias (three days from now), covered below.
a / às — clock times and specific points
Clock times take a (which contracts with the feminine as horas, giving às). Noon and midnight take ao/à.
O filme começa às oito em ponto.
The movie starts at eight on the dot. (a + as = às)
Vamos almoçar ao meio-dia?
Shall we have lunch at noon? (a + o = ao)
A reunião foi remarcada para a uma da tarde.
The meeting was moved to one in the afternoon. (singular hour: à uma → here 'a uma' after para)
Because horas is feminine plural, every plural hour gets the grave accent: às oito, às dez, às vinte. Singular uma hora gives à uma.
de — parts of the day and the from/to span
For in the morning / afternoon / evening / at night, Portuguese uses de with no article: de manhã, de tarde, de noite, de madrugada. De ... a / às also draws a span from one point to another.
Eu estudo melhor de manhã, de tarde fico sem foco.
I study better in the morning; in the afternoon I lose focus.
A loja abre das 8 às 18.
The store is open from 8 to 6. (de + as = das, a + as = às)
Trabalhei de segunda a sexta sem parar.
I worked Monday to Friday nonstop.
Note de manhã (no article) versus na manhã de segunda (a specific morning takes em + article). English uses in the morning for both; Portuguese distinguishes the general habit (de manhã) from the specific occasion (na manhã de...).
por and durante — duration
Por and durante both express "for / during" a stretch of time. Por often implies an intended or bounded duration; durante simply marks the span. In casual speech the duration is frequently left unmarked (morei lá dois anos).
Vou ficar em Salvador por duas semanas.
I'm going to stay in Salvador for two weeks.
Durante a pandemia, quase ninguém saía de casa.
During the pandemic, almost no one left the house.
desde and até — starting point and endpoint
Desde marks when something started and continues (since); até marks the endpoint (until). Together they bracket an open or closed interval.
Moro aqui desde 2015.
I've lived here since 2015.
Fica acordado até tarde estudando.
He stays up late studying. (até = until/up to)
Trabalho de casa desde a segunda até a sexta.
I work from home from Monday until Friday.
antes de and depois de — before and after
These compound prepositions take a noun or an infinitive, and the final de contracts.
Escova os dentes antes de dormir.
Brush your teeth before sleeping.
Depois do almoço, bate aquela preguiça.
After lunch, that drowsiness hits. (de + o = do)
The big one: há (ago) vs. daqui a (from now)
This is the trap English speakers fall into constantly. To measure a distance into the past, Portuguese uses há (or its colloquial twin faz). To measure a distance into the future, it uses daqui a. English uses ago for the past but the same in for the future, so learners reach for em in both directions — and get the future-distance wrong.
| Direction | Portuguese | English |
|---|---|---|
| Past distance | há dois anos / faz dois anos | two years ago |
| Future distance | daqui a dois anos | two years from now / in two years |
| Within a window | em dois anos | within two years |
Eu me formei há cinco anos.
I graduated five years ago. (há = ago)
A gente se conheceu faz uns dez anos.
We met about ten years ago. (faz = colloquial for há)
A encomenda chega daqui a três dias.
The package arrives three days from now. (daqui a = from now)
Days of the week and dates
Days of the week take em + article (contracting to na/no), often dropped in casual speech. Dates take em.
A gente se vê na segunda, então.
See you on Monday, then. (em + a = na)
O show é no dia 12 de outubro.
The show is on October 12th. (em + o = no)
Common Mistakes
❌ Eu cheguei a dois anos.
Incorrect — 'ago' is há (or faz), never a.
✅ Eu cheguei há dois anos.
I arrived two years ago.
❌ Ele volta em uma semana. (meaning: a week from now)
Ambiguous/incorrect for 'a week from now' — use daqui a.
✅ Ele volta daqui a uma semana.
He comes back a week from now.
❌ O filme começa em oito horas. (meaning: at 8 o'clock)
Incorrect — clock time takes às, not em.
✅ O filme começa às oito horas.
The movie starts at eight o'clock.
❌ Eu estudo na manhã todos os dias.
Incorrect — the general habit is de manhã, not na manhã.
✅ Eu estudo de manhã todos os dias.
I study in the morning every day.
❌ Nasci no 1998.
Incorrect — bare years take em, no article.
✅ Nasci em 1998.
I was born in 1998.
Key Takeaways
- Em: years, months, seasons (with article: no verão), and "within X time."
- A/às: clock times — às oito, ao meio-dia. Plural hours always carry the grave accent.
- De: general parts of the day — de manhã, de tarde, de noite — and de...a spans.
- Há / faz = "ago" (past distance); daqui a = "from now" (future distance). Never use a alone for "ago."
- Days take em + article: na segunda, no domingo.
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Start learning Portuguese→Related Topics
- Prepositions of PlaceA1 — The Brazilian Portuguese system for location — em (na/no) as the workhorse, plus a, de, entre, sobre/sob and the compound set (em cima de, atrás de, perto de) — and the unpredictable country-article quirk: no Brasil but em Portugal.
- Preposition 'Em': In, On, AtA1 — How 'em' collapses English in/on/at into a single preposition for location and time — its obligatory contractions (no, na, nele, nisso) and the verbs that take it.
- Preposition 'Desde': Since, FromB1 — How 'desde' marks the starting point of a span in time or space ('since', 'from') in Brazilian Portuguese, why it pairs with the present tense, and how 'desde que' splits between indicative and subjunctive.
- Preposition 'Até': Until, Up To, EvenA2 — How 'até' marks a spatial or temporal limit ('up to', 'until') and doubles as the adverb 'even' in Brazilian Portuguese — plus the optional crase in 'até a / até à'.
- Prepositions: OverviewA1 — A map of the Brazilian Portuguese preposition system, the obligatory contractions with articles and pronouns, and why prepositions almost never map one-to-one to English.